Tractor loaders



Oct 1, 1963 R. l.. BEYERsTEDT ETAL 3,105,603

TRACTOR LOADERS 3 Sheets-Sheet l Filed May 28, 1959 OC- l, 1963 R. BEYERSTEDT ETAL 3,105,603

TRACTOR LOADERS Filed May 28- 19552 y 3 Sheets-Sheet 2 Ocfl, 1963 R. 1 BEYERSTEDT TAL 3,105,603

TRACTOR LoADERs l Filed May 28. 1959 s sheets-sheet s Ezznonsu' Beyens'zeci @fallas C'. aedgelerJr. D n 5", Sracer United States Patent() 3,165,603 TRACTR LOADERS Ralph L. Beyerstedt and Salins C. Laegeler, Jr., Libertyville, and Don S. trader, Mount Prospect, lil., assignors to The Frank G. Hough Co., a corporation of Illinois Filed May 28, 1959, Ser. No. l6,513 12 Claims. (Cl. 21d- 140) This invention relates generally to tractor loaders, and more specifically to certain hydraulic circuits and valving in a -tractor loader having a pair of hydraulic rams or motors `acting in concert so that the hydraulic fluid pressure available -for operation of `the rams may be alternatively directed to one or simultaneously to both hydraulic rams.

In the art of tractor loaders it is a rather common construction -to provide a pair of hydraulic rams so connected that they operate together to perform some loader function. This is `generally done for reasons of economy and ease of design, although generally one cylinder of twice the size of each of the pair of cylinders could be substituted therefor. Further, it is common in the tractor loader art to provide a single hydraulic fluid pump of a substantially constant volume for operation of the various hydraulic rams of the loader mechanism. With such arrangements the speed of extension and retraction of the hydraulic rams is fairly constant under most conditions of loading. As the loading on the various members of a tractor loader can greatly vary, it is sometimes desirable to extend the hydraulic rams at a substantially greater sneed under conditions of relatively light loading. The present invention -accomplishes this result by providing certain hydraulic circuits and valving such that when the loading is light enough so that one hydraulic ram can provide suicient force to act against the load, means is prow'ded for directing the available hydraulic fluid to one of the hydraulic rams to provide for operation thereof at a speed which is substantially twice the speed of operation of the rams when both are supplied with the available hydraulic iluid under pressure.

Therefore it may be seen that the object of the present invention is to provide in a tractor loader having a pair of hydraulic rams of the same function, means for alternatively delivering hydraulic fluid from a single hydraulic pump to one tof the hydraulic rams or sirnultaneously to both of the hydraulic rams.

lt is another object of the present invention to provide in a tractor loader having a pair of hydraulic rams of the same function, means automatically operating responsive to the loading on said hydraulic rams for directing the available hydraulic iluid under pressure to one of the hydraulic rams or simultaneously to both hydraulic rams dependent upon the degree of loading.

It is a further object of the present invention to provide certain hydraulic valve and circuit means for the bucket pivoting rams `of a tractor loader which may be operated to ldirect the available hydraulic fluid under pressure to one of the hydraulic rams to cause a relatively rapid pivoting of the bucket or simultaneously to both of the hydraulic rams to cause a relatively slower pivoting of the bucket but lwith the application of a correspondingly greater force applied thereto.

It is a further object of the present invention to provide a certain hydraulic circuit for a tractor loader having a pair of rams having the same function wherein a 'valve may be used therein to deliver the available hydraulic fluid under pressure to one of the hydraulic rams or simultaneously to both of the hydraulic rams and providing for the delivery of relatively low pressure hydraulic fluid to the hydraulic ram which is not connected to high pres- Patented Oct. 1, 1963 2 sure hydraulic fluid source in order to keep bo-th sides of the piston of that ram tlled With hydraulic fluid.

Other objects and features of the present invention will be apparent upon 4a perusal of the following speoitication and drawings of which:

FIGURE l is -a side elevational view of a tractor loader constructed according to th-e present invention;

FlGURE la is a schematic drawing of -a hydraulic circuit for operation of .the present invention;

FIGURE 2 is a partial top plan View of the trac-tor loader shown in FIGURE l, showing the linkage means for pivoting the bucket and the directions of hydraulic lluid ilow when hydraulic iluid under pressure is applied to only one of the rams;

FlGURE 3 is a view similar to FIGURE `2 except for its showing of the directions of hydraulic fluid flow when hydraulic `fluid under pressure is simultaneously supplied to both of the hydraulic rams, Iand EFIGURE 4 is an enlarged lcross sectional View of the valve shown in FIGUR-E 2 and FIGURE 5 is an enlarged cross sectional View of the valve shown in FIG- URE 3.

The present embodiment is the preferred embodiment, but it is to be understood that changes can be made in the present embodiment by one skilled in the art Without departing from the spirit and scope of the present invention.

-For a general description of the present invention reference is made to the drawings. The specic tractor loader shown is only one of many types that can be used in the present invention. ln the tractor loader shown, a bucket is pivotally carried in a boom structure and is pivot-ally moved relative to the boom by a pair of hydraulic rams operating through a lever and linkage arrangement. The pair of hydraulic rams are pivotally carried on the tractor at their head ends and are both pivotally connected to the leve-r and linkage arrangement at their rod ends so that if hydraulic fluid under pressure is applied to one of the hydraulic rams to extend or retract that ram, the lother ram is identically moved by the lever and linkage arrangement by which the rams are mechanically interlocked. When hydraulic tluid under pressure is supplied to both of the hydraulic rams, it may be seen that both will operate to move the linkage and lever arrangement and pivot the bucket. As the pair of hydraulic rams are of the same size, it may be seen that with a source of hydraulic fluid under pressure delivering a constant volume of uid, the connection 'of that source of hydraulic fluid to only one of the rams will cause the lever and linkage arrangement to be moved at a speed which is twice that when the source of hydraulic lluid is delivered to both hydraulic rams, and the force applied is one-half `of that when the source of hydraulic lluid is connected to both of the hydraulic rams. The hydraulic circuits and valving of the present invention provides that in one operated position of the valving, hydraulic fluid under pressure is directed in either direction through one of `the bucket pivoting rams with the ro-d end of the other hydraulic ram connected to its head end. In another opera-ted position of the hydraulic circuits and valving, hydraulic iluid is directed in either direction simultaneously through both bucket pivoting rams. Although it is contemplated that a manually operated valve could be used, the present embodiment of the invention discloses a pressure responsive valve which will automatically operate When the loading on the bucket is relatively light to connect the high pressure hydraulic fluid .to only one of the bucket pivoting rams and permitting the other hydraulic ram to follow the movement of .the lirst by interconnecting each end of that ram, and further automatically operating when the loading on the bucket is relatively heavy to connect the source of hydraulic ilu-id under pressure to both ofsaid bucket pivoting rams for joint operation thereof in either direction.

rturning next to a detailed description of the present invention continued reference is made to the drawings. T he tractor loader of the present embodiment comprises a frame l@ supported on wheels 11 with the `fratrie l@ carrying an engine compartment l2, at the rearward end thereof, an operators compartment 13 substantially at the longitudinal center of the frame lil and an open platform portion at the forward end thereof. A pair 'of sometriangular plates ld yare provided on 4the open platform portion of the tractor on each side thereof and are mounted thereon to upstand therefrom. A boom 15 comprising duplicate boom arms is pivotally connected at one end thereof to the upper ends of .the plates 14 by means of pins i6. The boom 15 extends forwardly of the tractor and at the other end thereof is pivotaliy connected to a digging bucket i7 by means of pins i8. The boom is raised and lowered by la pair of hydraulic rams i9I mounted one on each side ofthe tractor. Each of the hydraulic rams i9 is pivotally connected to -a flange 2t? by means of la pin 21. Each of the anges 2@ is secured to the frame lil to depend therefrom. The rod end of each hydraulic ram l? is pivotally connected to one of the boom arms of the boom 1S intermediate the ends thereof by means of pins 22. Thus it may be seen that as the hydraulic rams i9 are extended the boom 15 is raised and as these rams are retracted the boom is lowered about the pivotal aXis of pins 16.

'l` he linkage means providing for pivoting of the bucket Vl relative to the boom l5 comprises a pair of hydraulic rams 23, a lever assembly 24 and a pair of links 25. The lever `assembly 2d comprises a pair of levers 26 which are secured intermediate their ends on each end of a cylindrical member 27 -to `form an integra-l assembly. The cylindrical member 27 Kis rotatively carried on a pin 28 which is secured between the arms of the boom intermediate the ends thereof. The upper end of each of the levers 26 lis pivotally connected to the rod end of 'one of the hydraulic rams 23 by means of a pin 29. The hea-d end of each of the hydraulic rams v23 is pivotally connected to a lange 3h by Imeans of a pin 3l. Each of the flanges 30 is mounted on a plate 32 which is secured to the opstanding plates 14 across the forward marginal edges thereof. The lower end of each of the levers Z6 is pivot-ally connected to one of the links by means of `a pin 33. The other end of each of the links 25' is pivotally connected to flanges 34 mounted on the rear wall of the bucket 17 by means of pins 35. The pins 35 are spaced upwardly yfrom the pins 18. Thus it may be seen .that when the hydraulic rams 23 are extended and retracted, the lever assembly 24 is pivoted to in turn move the links 25 to cause a pivoting of the bucket 117 about the axis of pins i8. lt may `further be seen that since the lever assembly 24 of levers 26 and cylindrical member 27 is a rigid unitary assembly, the extension and retraction of hydraulic rams 23 must always be in unison. One of the rams Z3 cannot be extended while the other is retracted.

One suitable hydraulic circuit for operation of the hydraulic rams i9 and 23 is shown schematically in PIG- URE la. A reservoir ila, pump 12a and a hydraulic main valve or control valve 13a are interconnected by a return conduit 14a, suction conduit 15a and supply conduit ida. The head end of the hydraulic rams 19 are parallel yconnected through a conduit llSa and at the other end are connected to the hydraulic main valve 13a. Similarly the rod end of the hydraulic rams 19 are parallel connected to a conduit .17a at one end `and at the other end thereof the conduit I17a .is connected to the hydraulic main valve i311. The conduit dll connected at one end to the valve i3 and the rod end of one of the other hydraulic rams 23 is connected at the other end to the hydraulic main valve i3d. The conduit 41 connected at one end to the conduits i4 and 45 is connected at the 4 other end to the hydraulic main valve 13a. Two valve spools 2da and Zla are provided within the hydraulic main valve 13a such that the one valve spool 20a selectively directs pressure uid under pressure from the supply conduit 16a to the conduits 17a and 18a for operation ot' `the hydraulic rams i9. The other valve spool f Zia selectively directs pressure lluid under pressure from the supply conduit 16a to either conduit 40 or 41 for the operation of the hydraulic ram 23 yand the valve 43. i

lt is to be understood that the hydraulic main valve 13a is of the open lcenter type construction as the preferred for-m and that any suitable means can be provided for selectively moving the valve spools Zita and lZia for operation of the hydraulic rams i9 land 23. further understood that when the valve spools 20a and Ela are moved from their non-operative position to an operative position such that pressure duid under pressure fis selectively directed to the conduits 17a and 40* the other conduits 18a and 4l are vented to the reservoir `11a through the return conduit Ma.

As previously mentioned one end of conduits liti and 41 partially shown in FIGURES 2 and 3 are connected tothe main hydraulic valve 13a so that high pressure hy-` draulic fluid from the pump 12a Iand low pressure hydnaulic' fluid to the reservoir lla may tbe directed through conduits 49 and 4i in the indicated directions of either the solid lines or `dotted lines. The other end of conduit d@ is .connected into conduit 4Z intermediate the ends thereof. `One end of conduit 42 is connected to the krod end of one of the hydraulic rams 23 and the other end of conduit 42. is connected to valve 43 at what will be referred to in the claims las the lirst port. The other end of -conduit 4l is connected into conduit 441 intermediate the ends thereof and each end of conduit d4' is connected to the head end of one of the hydraulic rams 2.3i. Conduit d5 is connected between conduit 44 and valve 43 at what will be referred to in the :claims as the second port, and conduit 46 is connected between the rod lend of the other hydraulic ram 23 and valve 43v at what will be referred to in the claims as the third port.

The valve 43, which is shown in its two operated positions in FIGURES 4 and 5, is shown somewhat diagrammatically therein. The valve housing lor body 47 is provided with a valve bore 43 in which a valve spool 49 is siid'ably canried. @ne end of the valve 'bore i8 is closed by a wall 50 and the other end thereof is .closed by a wall 51. A reduced vannular' section or shoulder 52 is provided in the valve bore 4S adjacent the end wall 51 and the shoulder 52 in abutting one end of the valve spo-ol 49 `determines one operated valve position of the valve 43.

A compressed coil spring 53 is provided in the other end of fthe valve bore 443 between the end wall 50 and the other end :of the valve spool i9 to bias the valve spool 49 against the shoulder 52. End wall Sil is provided with a conduit 54 connected therethrough and to the reservoir designated with the numeral 55 to drain any fluid accumulations from the chamber defined iby the end wall 50 and the cooperating end of the valve spool 49. The end wall 51 is also provided with an opening therethrough, however, an orice 56 is formed in this opening. The orifice 56 is of a size suciently small to permit the development of iluid pressures in the chamber delined by the end wall 51 and V the valve bore 4S to permit the valve spool 49 to return tothe first position under the bias of spring 53. The valve spool i9 is formed to have two lands 59 and 60 separated by a reduced section or annular groove 61. The valveV bore 4S is provided with three annular grooves 62, 63 and 6d. The annular grooves 62, 63 and 64 yand the lands 59 and `60 of the valve spool 49 are so positioned that in the lirst position of the valve, that in which the valve spoolk It is to be 49 abuts the shoulder 52, annular groove 64 is connected in tree lluid communication with annular groove 63 by the reduced section 61 `of the valve spool 49 and annular groove 62 is blocked by the land 59 of valve spool 49, and so that when the valve spool 49 is moved to the second position, that wherein the valve spool is moved toward end wall 50 until the coiled spring 53 is substantially completely compressed, the l-and 60 will rst block annular Igroove 64 after which the annular groove 62 will be connected in tree fluid communication with annular lgroove 63 by the reduced section 6l of valve spool 49. Annular Igroove 62 is connected through the valve body 47 and the lirst port to conduit 42. Annular groove 63 is connected .through the valve body 47 and the third port to conduit 46, and annular 4groove 64 is connected through the valve body 47 land the second .port to conduit 45.

Valve 43 further includes 'four one-way or check valves 66, 67, 63 and 69. Check valve 66 comprises a valve chamber 70 having a valve seat at the inner end thereo-'f cooperating with a ball 71 and connected by passageway 72 to annular groove 62. 'Ihe ball 71 is adjustably biased against the valve seat by the coiled spring 73 and the set screw 74 threaded into the router end of the chamber 7 il. 'Ihe valve chamber 70 is connected in tree fluid cornmunication with the reduced portion of the valve bore 48 vat the end wall 5l by a passageway 75. Thus it may be seen that when the fluid pressure in conduit 42 and annular groove 62 attains 'a pressure sufliciently high enough to unseat the ball 71, hydraulic fluid will flow from conduit 42, through passageway 72, through valve chamber 70, and passageway 75 to the reduced section of the valve bore 48 at end wall 5l.

The one-way valve 67 is substantially identical in construction to that of valve 66, having a valve chamber 77 having its inner end connected to passageway 78, and a ball 79 biased to close the end of passageway 78 by a coiled spring hthe bias of which is adjusted by the set screw 81 threaded into the router end of valve chamber 77. Valve chamber 77 is also connected in free iluid communication with the reduced section of the valve bore 48 at the end wall 5l and this is accomplished by a passageway 82 formed through the valve body 47. The check valves 68 and 69 are both mounted in the `other end of passage-way 78. Check valve '68.y which comprises ball E3 Iand compressed coiled spring `S4- is -connected to oonduit 46 and annular groove 63 Iby passageway 85. Check valve 68 prevents any hydraulic iluid in passageway 78 from flowing into conduit 46 and annular groove 63 but permits iluid to flow in the opposite direction. Check valve 69 comprises -ball S7 and compressed coiled spring 88. The :check valve `69 is con-nected to lannular groove 64 by ya short unnumbered passageway. Check valve 69 will operate to prevent any hydraulic fluid ilow firom passageway 78' into annular groove 64 but will permit hydraulic uid to flow in the opposite direction.

Turning next to a detailed description of the operation of the present invention in order that the construction thereof may be more readily understood, continued reference is made to the drawings. Assuming irst that it is desired to pivot the bucket 17 clockwise as viewed in FIGURE l such as in dumping or forcing the cutting edge of Ithe bucket downwardly into some load, this operation requires a retraction of the hydraulic rams 231. Further considering that the loading upon the bucket -is relatively light such as would generally occur in a dump-ing operation, the pertinent iigures yare FIGURES 2 `and 4 of the drawings. The path taken by the hydraulic iluid under these conditions Vis shown in the solid line arrows in FIG- URES Zand 4. The main hydraulic valve 13a is operated to direct high pressure hydraulic fluid to conduit 40 and to connect conduit 41 to the reservoir 11a. The high pressure hydraulic iluid will then flow through conduit 40 land 42 into the rod end of one of the hydraulic rams 23. Hydraulic iluid will also flow from the head end of that hydraulic ram 23, through conduit 44, and conduit 41 to the reservoir lla. As the one hydraulic ram is caused to retract by the ilow of hydraulic iluid, the lever assembly 24 will be pivoted and this in turn will cause the other hydraulic ram 23 to be retracted. As the other hydraulic ram 23 is retracted, hydraulic iluid will ilow from the head end thereof, through conduit 45, into la valve 43, annular groove 64, valve bore 48 about the reduced section 61 of the valve spool 49, annular groove 63, and conduit 46 to the rod end of that hydraulic ram. The excess of hydraulic fluid which is substantially equal to the volume of the piston rod thereof, will ow through conduit 44 and conduit 4l to the reservoir. As the hydraulic iluid ilowing through the valve is of a relatively low pressure, the one way valve 67 will not be operated.

Assuming next, the same operation of the main hydraulic valve 13a, that for dumping or clockwise pivoting of the bucket las viewed in IFIGURE l, but that la certain substantially larger loading is encountered by the bucket, which will .also result in a reaction against retraction on the piston of the hydraulic ram 23 which is being supplied high pressure hydraulic fluid. This reactive force will cause the hydraulic fluid pressure in conduit 44B to rise and when the pressure reaches the value -for which the valve 66 has been adjusted, the hydraulic fluid pressure acting through passageway 72 will unseat ball 7l to permit hydraulic iluid to flow through chamber 70, and passageway 75 into the reduced section of the valve bore 48 at end wall 5l. This lhydraulic iluid under pressure operating lagainst the end of the valve spool 49 will move the valve spool 49 compressing the coiled spring 53. The first action or" the valve spool 49 will be a blocking of the conduit 4S by the land 60. Further operation will interconnect conduits 42 and The valve 43 will then be positionedas shown in lFIGURE 5, and the hydraulic `fluid ow will be that shown in the solid line arrows of FIGURE I3. Hydraulic lluid will flow through conduit 46, and into conduit 42 wherein the flow will be divided, one portion entering the rod end of one of the hydraulic rams 23, with the other portion `flowing from conduit 42 into valve 43, `annular .groove 62, through valve bore 43 about the reduced section 6l of the valve spool 49, annular groove 463 yand conduit 46 to the rod end of the other hydraulic ram 23. Hydraulic iluid `from the head end of the first hydraulic ram 23 will ow through conduit 44- and 41 to the reservoir 11a. As conduit 45 is now blocked, hydraulic lluid from the head end of the other hydraulic ram 23 will low from conduit 44 into conduit 41 to the reservoir llo. Since the hydraulic iluid from conduit 40 is divided to enter the rod end et both hydraulic rams 23, it may be seen that with each hydraulic ram 23 receiving one-half of the volume delivered, the hydraulic rams will retract at substantially one-half of the speed -a-t which a retraction took place as above described under a light load. Although the speed of retraction of the hydraulic rains 23 is substantially one-half of that of the light load, the force applied by the hydraulic ram 23 to the lever Iassembly 24 will be substantially twice that which is applied upon the bucket during light loading. In the present invention the valves 67 and 66 are so adjusted that the force required to unseat valve 67 is substantially less than that required to unse-at valve 66. A pressure setting for valve 67 which is about one-half of that for which valve 66 is set has been found satisfactory. Since there is an immediate huid pressure drop when conduit 42 is interconnected with conduit 46, valve 66 will close. However, before valve 66 can close, the hydraulic iluid under pressure will in ilowin g through passageway open check valve 68 and valve 67 to admit hydraulic iluid through passageway S72 into the reduced section of the valve bore 48 at the end wall 51 to maintain the valve 43y in the position shown in FIGURE 5. Check valve 69 will -function to prevent yany hydraulic fluid in passageway 7 8 from flo-wing into annular groove 64 which is connected to conduit 45. If the load on the bucket lightens sufficiently to permit valve 67 to close, the fluid in the valve bore 48 at the end Wall l will drain on through the orifice 56 permitting the spring 53 to return the valve spool 49 to a position such as shown in FIGURE 4 again switching the operation of the hydraulic rams 23 to one hydraulic ram as previously described in reference to FIGURE 2.

Assuming next that it is desired to pivot the bucket 17 rearwardly cr counterclockwise as viewed in FIGURE 1, such as in breaking away a loaded bucket vfrom some material being worked, and assuming that the loading on the bucket is relatively light, the hydraulic luid flow will be directed as shown in the dotted line arrows in FIGURES 2 and 4. Hydraulic duid under pressure entering at conduit 4l will flow into conduit 44. From conduit 44 some amount of duid will enter the hydraulic ram 23 to which conduit 46 is connected. The other portion of the hydraulic fluid will flow through conduit 44 to enter the head end of the other or rst hydraulic ram Z3. Hydraulic iluid from the rod end of the first hydraulic ram will enter conduit 42 and from conduit ft2 will ow through conduit 40 to return to the reservoir `lla. Additionally, hydraulic iluid from the rod end of the other hydraulic ram 23 will flow through conduit 46 and into valve 43, annular groove 63, through the valve bore 43 and abou-t the reduced section 6l of the valve spool 49, annular groove 64 and through conduit 45. From conduit 45 the hydraulic duid may ilow through conduit 44 and into the head end of that hydraulic ram 2.3 to Iaid in lling the cylinder as that hydraulic ram 23 follows the movement of the first hydraulic ram in extending. Thus it lmay be seen that the hydraulic lluid under pressure delivered through conduit 4l is used to extend the rst hydraulic ram 23 and replace in the other hydraulic ram a volurne of uid equal to the volume of the piston rod thereof. Since conduit 42 is connected to the reservoir, the uid pressure therein will not be suflicient to cause any operation oi valve 66. Further, at this time the hydraulic iluid pressure in conduit 46 and annular groove 64 will not be high enough to operate Athe valve 67.

Assuming next that the bucket 17 is continued to be pivoted rearwardly, but that the loading thereon increases substantially or suiiciently high enough to operate hydraulic valve 67. Valve 67 will then operate, the ball 79 being unseated to permit hydraulic fluid to ilow therethrough and through passageway 82 to the reduced section in the valve bore 48 at the end wall 51. This hydraulic iiuid under pressure inthe valve lbore 43 will cause valve spool t9 to be moved to a position such as shown in FIGURE 5 with a consequent fluid flow such as shown in the dotted line arrows in FIGURES 3 and 5. The increased loading on the bucket will result in a substantially increased pressure in conduit 45 and annular groove 64,

which pressure will be applied through the check valve 69 to operate the valve 67 as previously described. As the valve spool 49 is moved to the position such as shown in FIGURE 5, annular groove 64 is blocked from duid communication with annular -groove 63 before annular grooves 62 and 63 yare connected in free fluid communication. The continued high pressure of the hydraulic iluid in conduit 45 will continue to be `applied about land 6i) of valve spool 49 and through check valve 69 to valve 67 maintaining hydraulic Huid pressure on the end of the valve spool 49. Hydraulic fluid will then flow through conduit 4l and from `conduit 44 into hydraulic rams 23. Hydraulic fluid from the rod end of the iirst hydraulic ram 23 will how into conduit 42 and from conduit 42 into conduit di). Hydraulic fluid from the rod end of the other hydraulic ram 23 will ilow through conduit 46 into valve 43, annular groove 63, through valve bore 4S about the reduced section 6l of valve spool 49, annular groove 62, conduit 42 to and through conduit 4t). Thus it may be seen that the delivered hydraulic uid under pressure from conduit 4d is now equally divided between the two hydraulic rams 23 causing a reduced speed of operation of the hydraulic rams at substantially twice the applied yforce over that which occurred for the above described single 8 operation of the iirst hydraulic ram 23. If the hydraulic fluid pressure in conduit 45 drops below that necessary to maintain valve 67 operated, valve 67 will close and valve spool 49 will return lto the position sho-wn in FIGURE 4 under the bias of coiled `spring 53 as the Huid gradually passes through the oriiice 56 to the reservoir 55.

Having described the invention what is considered new and desired to be protected :by Letters Patent is: *Y

l. In a tractor loader having a source of constant volume hydraulic duid under pressure and a fluid reservoir, a pair of hydraulic lrams mechanically interlocked for n performing the same material handling function, a hydraulic valve operable to two positions, hydraulic fluid conduit ymeans interconnecting said source of hydraulic duid, said reservoir, the head and rod ends of said hydraulic rams and said valve, said hydraulic -uid conduits being connected and said hydraulic valve Abeing formed so that in the iirst operated position of said hydraulic valve, the head and rod ends of one of said hydraulic rams are respectively connected to said source of hydraulic iuid and said reservoir andthe head and rod ends of the other of said hydraulic rams are connected in free fluid communication, and so that when said hydraulic valve is operated to the second position the head and rod ends of both of said hydraulic rams are respectively connected to said source of hydraulic fluid and said reservoir.

2. In a tractor loader having a source of constant volume hydraulic Kfluid under pressure and a reservoir, a pair of hydraulic rams mechanically interlocked for performing the Same material handling function, a hydraulic valve operable to two positions, hydraulic fluid conduit mea-ns connected between said source of hydraulic uid, said reservoir, the head and rod ends of said hydraulic rams and said valve, said hydraulic'iluid conduit means being connected and said valve being formed so-that in the rst operated position of said valve, the head and rod ends of one of said hydraulic rams are separately connected to said source of hydraulic. uid and said reservoir and the head and rod ends 'ofV the other of said hydraulic rams are interconnected inV means formed in said valve andoperating responsive to any loading on said hydraulic rams below a certain amount for operating said hydraulic valve to said iirst position and operating responsive to any loading @on said hydraulic rams above said certain amount for operating said hydraulic valve to said second position.

3. In a tractor loader having a source of constant volume hydraulic fluid under pressure and a reservoir, a pai-r of hydraulic rams mechanically interlocked for performing the same material handling function, a hydraulic valve comprising a valve spool slidable to iirst and second operated positions, and a coiled spring positioned therein to bias said valve to said iirst position, hydraulic fluid conduit means connected between said source of hydraulic diuid, said reservoir, the head and rod ends of tsaid hydraulic rams and said valve, said hydraulic fluid conduit means being connected and said valve being formed so that in said lirst operated position of said valve, the head and rod ends of one of said hydraulic rams are separately connected to said source of hydraulic fluid and said reservoir and the head and rod ends of the other of said hydraulic rams are interconnected in free liuid communication, and so that when said valve is operated to said second position, the head and rod -ends of both oi' smd hydraulic rams are separately connected to said source of said hydraulic iluid and said reservoir, and adjustable check valve means formed in said Vvalve and operating responsive to .hydraulic fluid pres-V sponsive to any hydraulic fluid pressures in said valve above said certain amount for admitting hydraulic lluid under pressure to one end of said valve spool to move said valve spool against the bias of said coiled spring to operate said valve to said second position.

4. In a tractor loader, a boom pivotally mounted on said tractor and extending for-wardly thereof, a digging bucket pivotally carried on the outer end of said boom, linkage means pivotally connected between said tractor, said boom and said bucket for pivoting said bucket relative to said boom, said linkage means including a pair of hydraulic rams mechanically interlocked and operating to pivot said bucket relative to said boom, a source of constant volume hydraulic iluid under pressure for operating said pair of hydraulic rams, hydraulic circuit means including a hydraulic valve connected between said source of hydraulic liuid and said pair of hydraulic rams and being operable to one position to deliver substantially all of the available hydraulic iiuid from said source of hydraulic fluid to one of said hydraulic rams for operation thereof Iwhile interconnectin-g the head and rod ends of the other of said pair of hydraulic rams in free ilu-id communication whereby said other hydraulic ram 'will follow the operation of said one of said hydraulic rams, said hydraulic circuit means including said hydraulic valve being further operable to another position to deliver substantially all of the available hydraulic iluid from said source of hydraulic liuid simultaneously to both of said hydraulic rams for operation thereof.

5. In a tractor loader, a boom pivotally mounted on said tractor and extending forwardly thereof, a digging bucket pivotally carried on the outer end of said boom, linkage means pivotally connected between said tractor, said boom and said bucket for pivoting said bucket relative to said boom, said linkage means including a pair of hydraulic rams mechanically interlocked and operating to pivot said bucket relative to said boom, a source of constant volume hydraulic fluid under pressure for operating said pair of hydraulic circuit rams, hydraulic circuit means connected between said source of hydraulic fluid and said pair of hydraulic rams and being operable to one position to deliver substantially all of the available hydraulic fluid from said source of said hydraulic fluid to one of said hydraulic rams for operation thereof while connecting the head an-d rod ends of the other of said pair of hydraulic rams in free uid communication whereby said other -hydraulic ram will 4follow the operation of said one of said hydraulic rams, said hydraulic circuit means further operable to another position to deliver substantially all of the available hydraulic iluid from said s'ource of said hydraulic Huid simultaneously to both of said hydraulic rams for operation thereof, and one hydraulic valve lmeans within `said circuit operating responsive to any loading on said bucket below a certain amount for operating said hydraulic circuit means to said one position and operating responsive to any loading on said bucket above .said certain amount for operating said hydraulic circuit means to said another position.

6. In a tractor loader, a boom pivotally mounted on said tractor and extending forwardly thereof, a digging bucket pivotally carried on the outer end of said boom, linkage means pivotally connected between said tractor, said boom and said bucket for pivoting said bucket relative to said boom, said linkage means including a pair of hydraulic rams mechanically interlocked and operating to pivot said bucket relative to said boom, a source of constant volume hydraulic iluid under pressure for operating said pair of hydraulic rams, a hydraulic valve operable to two positions, a coiled compressed spring disposed in said valve for biasing said valve to the iirst operated position, adjustable hydraulic check valves formed in said valve and operating responsive to a centain predetermined hydraulic uid pressure for operating said hydraulic valve to the second position, hydraulic fluid conduit means interconnecting said source of hydraulic iluid, said pair of hydraulic rams and said valve, said hydraulic fluid conduits being connected and said hydraulic valve being formed so that in said rst operated position of said hydraulic valve, one of said hydraulic rams` is connected to receive substantially all of the hydraulic uid available from said source of hydraulic fluid and the head and rod ends of the other of said hydraulic rams are interconnected in free iluid communication, land so when said hydraulic valve is operated to said second position substantially all of the :available hydraulic iluid from said source of hydraulic fluid is simultaneously delivered to both of said hydraulic rams for operation thereof, said adjustable check valve means being connected to said hydraulic fluid conduits so that said v-alve is operated to said first position for any hydraulic fluid pressures in said valve below a certain amount and so that said valve is operated to said second position for lany hydraulic fluid pressures in said valve above said certain amount.

7. In a tractor loader, a boom pivotally'mounted on said tractor and extending forwardly thereof, a digging bucket pivotally carried on the outer end kof said boom, linkage means pivotally connected between said tractor, said boom and said bucket for pivoting said bucket relative to said boom, said linkage means including a pair of hydraulic rams mechanically interlocked and operating to pivot said bucket relative to said boorn, a source of constant volume hydraulic tluid under pressune for operating said pair of hydraulic ram-s, a hydraulic valve operable to two positions, hydraulic iluid conduit means interconnecting said source of hydraulic fluid, said pair of hydraulic rams and said valve, said hydraulic fluid conduits being connected and said hydraulic valve being formed so that in the rst operated position of said hydraulic valve, one of said hydraulic rams is connected to receive substantially all of the hydraulic fluid available from said source of said hydraulic fluid and the head and rod ends of the other of said hydraulic rams are interconnected in free iluid communication, and so that when vsaid hydraulic valve is operated to the second position substantially all of the available hydraulic fluid from said source of hydraulic fluid is simultaneously delivered to both of said hydraulic rams for operation thereof.

8. In a tractor loader, a boom pivotally mounted on said tractor and extending forwardly thereof, a digging bucket pivotally carried on the outer end of said boom, linkage means pivotally connected between said tractor, said boom and said bucket for pivoting said bucket relative to said boom, said linkage means including a pair of hydraulic rams mechanically interlocked and operating to pivot said bucket relative to said boom, a source of constant volume hydraulic fluid under pressure for operating said pair of hydraulic rams, a hydraulic valve operable :to two positions, hydraulic iiuid conduit means interconnecting said source of hydraulic Huid, said pair of hydraulic rams and said valve, said hydraulic fluid conduits being connected and said hydraulic valve being formed so that in the iirst operated position of said hydraulic Valve, one of said hydraulic rams is connected to receive substantially all of the hydraulic uid available from said source of said hydraulic fluid and the head and rod ends of the other of said hydraulic rams are interconnected in free lluid communication, and so that when said hydraulic valve is operated to the second position substantially all of the available hydraulic fluid from said source of hydraulic iluid is simultaneously delivered to both of said hydraulic rams for operation thereof, and means formed in said valve and operating responsive to any loading on said bucket below :a certain amount for operating said hydraulic valve to said iirst position and operating responsive to any loading on said bucket above said certain amount for operating said hydraulic valve to said second position.

9. In a tractor loader having a source of constant volume hydraulic lluid under pressure and a reservoir, a

pair of hydraulic rams mechanically interlccked for performing the same material handling function, first and second hydraulic fluid conduits alternately connectable at one end of each thereof to said source of hydraulic fluid and said reservoir, a hydraulic valve having three ports, means connecting the other end of said first conduit in parallel to the rod end of one of said hydraulic ram-s and to the first port of said valve, means connecting the other end of said second conduit in parallel to the head ends of both of said hydraulic rams and to the second port of said valve, mea-ns connecting the third port of said valve to the rod end of the other of said hydraulic rams, said hydraulic valve being formed so that in one operated position thereof, said first port is blocked and said second and third ports are connected in free fluid communication so that in a second operated position thereof said second port is blocked and said first and third ports are connected in free fluid communication.

l0. In a tractor loader having a source of constant volume hydraulic fluid under pressure and a reservoir, a pair of hydraulic rams mechanically interlocked for performing the same material handling function, first and second hydraulic fluid conduits alternately connectaole at one end of each thereof to said source of hydraulic fluid and said reservoir, a hydraulic valve having three ports, means connecting the other end of said first conduit in parallel to the rod end of one of said hydraulic rams and to the first port of said valve, means connecting the other end of said second conduit in parallel to the head ends of both of said hydraulic rams and to the second port of said valve, means connecting the third port of said valve to the rod end of the other of said hydraulic rams, said hydraulic valve being formed so that in one operated position thereof said first port is blocked and said second and third ports are connected in free fluid communication and so that in a second operated position thereof, said second port is blocked and said first and third ports are connected in free fiuid communication, means in said valve releasably maintaining said valve operated to said one operated position, fiuid pressure responsive means formed in said valve and operating responsive to a fluid pressure at said first port above a certain predetermined amount for operating said valve to said second operated position, and second fluid pressure responsive means formed in said valve and operating responsive to hydraulic fluid pressures at said second and third ports less than said certain predetermined amount for operating and maintaining said valve in said second position.

11. in a tractor loader as claimed in claim l0 wherein a digging bucket is provided and pivotally carried from volume hydraulic fluid under pressure and a reservoir, k

a pair of hydraulic rams mechanically interlocked for performing the same material handling function, first and second hydraulic fluid conduits alternately connectable at one end of each thereof to said source of hydraulic fluid and reservoir, a hydraulic valve having three ports, means connecting the other end of said first conduit in parallel to the rod end of one of said hydraulic rams and to the first port of said valve, means connecting the other end of said second conduit in parallel to the head ends of both of said hydraulic rams and to the second port of said valve, means connecting the third portof said valve to the end of the other of said hydraulic rams, said hydraulic valve comprising a valve bore having a valve spool slidably carried therein, said valve ports connected to said valve bore and said valve spool being formed so that in one position of said valve spool said first port is blocked and said second and third ports are connected in free fluid communication and so that in a second position of said valve spool, said second port is blocked and said rst and third ports are connected in free uid communication, a first coiled spring disposed within said valve bore and biasing said valve spool to said one position, adjustable check valve means connected between said three ports and said valve bore at the other end of said valve spool for admitting hydraulic fluid above certain pressures to said valve bore to move said valve spool to said second position.

References Cited in the file of this patent UNITED STATES PATENTS 2,292,278 Lorenz Aug. 4, 1942 2,590,454 Pilch Mar. 25, 1952 2,628,731 Reuter Feb. 17, 1953 2,732,963 Grubich Jan. 31, 1956 2,902,053 Seddon Sept. 1, 1959 2,912,007 johnson Nov. 10, i959 2,935,852 Russell May 10, 1960 

1. IN A TRACTOR LOADER HAVING A SOURCE OF CONSTANT VOLUME HYDRAULIC FLUID UNDER PRESSURE AND A FLUID RESERVOIR, A PAIR OF HYDRAULIC RAMS MECHANICALLY INTERLOCKED FOR PERFORMING THE SAME MATERIAL HANDLING FUNCTION, AS HYDRAULIC VALVE OPERABLE TO TWO POSITIONS, HYDRAULIC FLUID CONDUIT MEANS INTERCONNECTING SAID SOURCE OF HYDRAULIC FLUID, SAID RESERVOIR, THE HEAD AND ROD ENDS OF SAID HYDRAULIC RAMS AND SAID VALVE, SAID HYDRAULIC FLUID CONDUITS BEING CONNECTED AND SAID HYDRAULIC VALVE BEING FORMED SO THAT IN THE FIRST OPERATED POSITION OF SAID HYDRAULIC VALVE, THE HEAD AND ROD ENDS OF ONE OF SAID HYDRAULIC RAMS ARE RESPECTIVELY CONNECTED TO SAID SOURCE OF HYDRAULIC FLUID AND SAID RESERVOIR AND THE HEAD AND ROD ENDS OF THE OTHER SAID HYDRAULIC RAMS ARE CONNECTED IN FREE FLUID COMMUNICATION, AND SO THAT WHEN SAID HYDRAULIC VALVE IS OPERATED 